The invention relates to an effect yarn which is formed from an alternating line-up of webs and effects consisting of predetermined thickenings and to a method for producing such an effect yarn on an open-end rotor spinning machine, wherein the effect yarn is reconnected by means of a piecer after yarn interruptions.
During the production of yarn, as high a uniformity of the yarn as possible is generally aimed for within narrow tolerances. In contrast, for effect yarns, the non-uniformity of the yarn is characteristic. A yarn in which thick locations with predetermined larger diameters and with predetermined lengths, the so-called effects, are present is designated an effect yarn. The yarn sections located in between with a smaller diameter are designated webs. A specific, constantly recurring, intrinsically closed sequence of effects and webs in an alternating series of effect and web is called a yarn repeat. The repeat length is the sum of all effect lengths and web lengths. Effect yarns are becoming increasingly important. Areas of application are, for example, denim materials, materials for casual clothing and home textiles.
Effect yarns can also be produced on rotor spinning machines. In order to produce effects in the yarn on rotor spinning machines, the fiber feed to the opening roller of the rotor spinning device can be changed, for example, in that the speed of the draw-in rollers is varied.
When the thread run at open-end rotor spinning machines has been interrupted by a thread break or as a result of a cross-wound bobbin change or as a result of the cutting process after a detected, intolerable yarn defect, the thread has to be rejoined. A piecer of this type differs with regard to its diameter, in particular in the case of yarn with a diameter that remains the same, from the remaining spun yarn. The formation of piecers in rotor spinning is described, for example in DE 40 30 100 A1 or the publication, Raasch et. al. “Automatisches Anspinnen beim OE-Rotorspinnen”, MELLIAND Textilberichte April 1989, pages 251 to 256.
In order to carry out the piecing process, a piecing unit which can be moved along the rotor spinning machine is generally delivered to the respective spinning station. In this case, the normal thread run is changed at the spinning station for piecing and control of the yarn formation is taken over by the piecing unit. During piecing and the subsequent run-up of the rotor, the thread can be drawn off, for example, from the spinning rotor by draw-off rollers, which are controlled by the piecing unit. Until the operating rotor speed has been reached, the take-off speed follows the increase in the rotor speed. Once the spinning rotor has reached its operating speed, the thread is returned to the normal thread run at the spinning station. With the transfer of the thread, the piecing process is ended. Control of the yarn formation is taken over again by the control device of the spinning station or the associated group control. In the known production of effect yarn on open-end rotor spinning machines, the program for forming effects also starts up again from this time. Yarn with effect formation adjoins the piecing region. The piecing region downstream from the piecer, depending on the drawing, can be several meters, with high drawings up to five meters.